There have heretofore been known apparatus which generate singing voices by synthesizing voices of lyrics while varying a pitch in accordance with a melody. Japanese Patent Application Laid-open Publication No. 2008-170592 (hereinafter referred to as “Patent Literature 1”), for example, discloses a technique which, in response to MIDI messages being sequentially supplied from a performance data generation apparatus, sequentially updates a current singing position on the basis of prestored lyric data. Further, Japanese Patent Application Laid-open Publication No. 2012-083569 (hereinafter referred to as “Patent Literature 2”) discloses a technique which, in response to phonogram data being output, sequentially reads out scale note data from a melody storage area and synthesizes voices of phonograms indicative by the phonogram data and having scale notes (pitches) indicated by the scale note data read out from the melody storage area.
Further, in “The Development of a Text Input Interface for Realtime Japanese Vocal Keyboard” co-authored by Kazuhiko YAMAMOTO, Shota KAGAMI, Keizo HAMANO, and Kazuki KASHIWASE, Transaction of Information Processing Society of Japan, Vol. 54, No. 4, pp 1373-1382 (2013) (hereinafter referred to as “Non-patent Literature 1”), a keyboard musical instrument is disclosed which designates, one by one, characters of lyrics (lyrics characters) comprising Japanese alphabetical letters (or characters), while combining vowel keys, consonant keys and voiced sound symbol keys. Furthermore, in the overview and background of “Brother's Realtime Vocal Synthesis Performing System” by Noriyasu SAKODA in research bulletin of Nagoya University of Arts and Sciences, Art and Design Department, pp 21-33 (2013) (hereinafter referred to as “Non-patent Literature”), a musical instrument is disclosed in which a plurality of characters are allocated to a group of performance instructing buttons of an accordion and in which lyrics can be designated, one character by one character, through operations of desired ones of the buttons.
In the conventionally-known apparatus which generate voices on the basis of characters, such as singing voice generation apparatus, it has been difficult to designate desired characters through simple operations. More specifically, according to the disclosure of Non-patent Literature 1, lyrics are caused to automatically progress in synchronism with a progression of a music piece performance (tones). Further, according to the disclosure of Non-patent Literature 2, a melody is caused to automatically progress in synchronism with a progression of lyrics. Namely, according to each of the disclosed techniques in Non-patent Literature 1 and Non-patent Literature 2, voice generation of a character train is performed only in accordance with a progression of the lyrics. Thus, in each of the aforementioned prior art techniques, it is not possible to execute an ad lib performance with a desired melody while selecting characters in a different progression from the sequenced lyrics. Therefore, it is impossible to, for example, change and/or repeat voices of the lyrics in an ad lib fashion.
Further, although the prior art techniques disclosed in Non-patent Literature 1 and Non-patent Literature 2 allow characters of lyrics to be freely designated, the technique disclosed in Literature 1 is unsatisfactory in that it requires complicated character designating operations, and the technique disclosed in Literature 2 is unsatisfactory in that there are an extremely great number of character designating choices. Thus, with these techniques, it is difficult to perform selection operations such that desired lyrics can be generated at a practical progression speed of a music piece performance (tones).